Am I correct in assuming that a car that has a computer on it, that you should not use a knife switch on the car's battery terminal, the knife switches that are advertised in magazines like carparts.com? Also one should not disconnect a car's battery terminal in a effort to keep the battery from running down, but should keep the battery hooked to a float charger, right, if it has a computer in it?
There are gradations and degrees of electronics and sensors in vehicles. All other things being equal, the newer the vehicle, the more problematic it is to disconnect the battery without an OBD memory retainer because of the cascade effect of sensors and computers than can be affected.
Particularly in European cars (BMWs, Audis, Mercedes, etc.) this can be an expensive mistake, because even the battery itself has to be registered and programmed into the computer. And all of the information, even in non-European cars, such as those "Safety" and "Blind Spots" sensors have to be reprogrammed, and that's not a ten minute job. The reprogramming of all those devices often can be done only at the dealer, and it will cost hundreds of dollars.
Look, I have a 2008 Camry LE. If I disconnect the battery, the only thing I have to deal with is the relearn of idle and resetting of the clock. Much the same for my wife's 2013 Honda Fit, with the exception of unlocking the radio with a code.
Move up to 2020 or 2021, or even more sophisticated 2014 vehicles, with all that technology stuffed into the vehicle, it's an entirely different ballgame, so to speak. So, no, don't use something like a knife switch.
